#!/usr/bin/python # # Copyright 2024, The Android Open Source Project # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. # """A script to sign nanoapps for testing purpose on tinysys platforms.""" import argparse import ctypes import hashlib from cryptography.hazmat.primitives import hashes from cryptography.hazmat.primitives import serialization from cryptography.hazmat.primitives.asymmetric import ec from cryptography.hazmat.primitives.asymmetric import utils class HeaderInfo(ctypes.LittleEndianStructure): _fields_ = [ ("magic_number", ctypes.c_uint32), ("header_version", ctypes.c_uint32), ("rollback_info", ctypes.c_uint32), ("binary_length", ctypes.c_uint32), ("flags", ctypes.c_uint64 * 2), ("binary_sha256", ctypes.c_uint8 * 32), ("reserved_chip_id", ctypes.c_uint8 * 32), ("reserved_auth_config", ctypes.c_uint8 * 256), ("reserved_image_config", ctypes.c_uint8 * 256), ] def read_private_key(key_file, password): with open(key_file, "rb") as file: key_bytes = file.read() try: return serialization.load_der_private_key(key_bytes, password=password) except ValueError as e: pass # Not a DER private key try: return serialization.load_pem_private_key(key_bytes, password=password) except ValueError: pass # Not a PEM private key raise ValueError("Unable to parse the key file as DER or PEM") def main(): parser = argparse.ArgumentParser( description="Sign a binary to be authenticated on tinysys platforms" ) parser.add_argument( "private_key_file", help="The private key (DER or PEM format) used to sign the binary", ) parser.add_argument( "-p", "--password", type=str, help="Optional password encrypting the private key", ) parser.add_argument( "nanoapp", help="The name of the nanoapp binary file to be signed" ) parser.add_argument( "output_path", help="The path where the signed binary should be stored" ) args = parser.parse_args() # Load the binary file. binary_data = None with open(args.nanoapp, "rb") as binary_file: binary_data = binary_file.read() # Load ECDSA private key. password = args.password.encode() if args.password else None private_key = read_private_key(args.private_key_file, password) # Generate a zero-filled header. header = bytearray(0x1000) # Fill the public key. public_key_numbers = private_key.public_key().public_numbers() header[0x200:0x220] = public_key_numbers.x.to_bytes(32, "big") header[0x220:0x240] = public_key_numbers.y.to_bytes(32, "big") # Fill header_info. sha256_hasher = hashlib.sha256() sha256_hasher.update(binary_data) header_info = HeaderInfo( magic_number=0x45524843, header_version=1, binary_length=len(binary_data), binary_sha256=(ctypes.c_uint8 * 32)(*sha256_hasher.digest()), ) header_info_bytes = bytes(header_info) header[0x400 : 0x400 + len(header_info_bytes)] = header_info_bytes # Generate the signature. signature = private_key.sign(header[0x200:], ec.ECDSA(hashes.SHA256())) r, s = utils.decode_dss_signature(signature) r_bytes = r.to_bytes(32, "big") s_bytes = s.to_bytes(32, "big") header[:32] = r_bytes header[32:64] = s_bytes with open(f"{args.output_path}/{args.nanoapp}", "wb") as output: output.write(header) output.write(binary_data) if __name__ == "__main__": main()